Enamel Protectant and Repair Brushing Gels

ABSTRACT

Substantially aqueous-free, enamel protectant and repair brushing gels containing: stannous fluoride, calcium and a substantivity agent comprising: an emulsion of polydimethylsiloxane in a nonionic surfactant, wherein substantivity of said stannous fluoride and calcium into biofilm present on enamel is enhanced through calcium binding shifting from bidentate to monodentate in the presence of stannous fluoride; and said brushing gels have substantially improved, enamel protectant factor (EPF) and enamel repair factor (ERF) values compared to fluoride brushing treatments with comparable or higher fluoride levels.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent application Ser. No. 13/651,044, which was filed on Oct. 12, 2012, entitled “Improved Remineralizing and Desensitizing Compositions, Treatments and Methods of Manufacture”; which specification, including Examples, Tables and Drawings, are hereby incorporated by reference, in total into the present application. This application is co-pending with U.S. patent application Ser. No. ______, filed on Apr. 11, 2014, titled “Methods for Protecting and Repairing Enamel”.

FIELD OF THE INVENTION

The present invention is directed to advances in enamel protectant and enamel repair, aqueous-free, stannous fluoride, brushing gels; whereby the protectant and repair ingredients are substantive to enamel surfaces, thereby extending the protecting and repairing processes with improved stannous fluoride effectiveness. Key protectant and repair combinations for the brushing gels of the present invention comprise: stannous fluoride and calcium in aqueous-free, substantivity agents.

BACKGROUND OF THE INVENTION

The use of fluoride in anticaries drug products, marketed in the U.S., is carried out under the guidance of the FDA's Fluoride Monograph, 21 CFR 355.10 (revised Apr. 1, 2012).

TABLE 1 Concentration and Dosage of Stannous Fluoride in Dentifrice/Rinse/Gel products according to the Federal Register 21 CFR 355.10 Dentifrices Dentifrices containing 850 to 1,150 ppm theoretical total fluorine in a gel or paste dosage form. Stannous fluoride 0.351 to 0.474% with an available fluoride ion concentration = 700 ppm for products containing abrasives other than calcium pyrophosphate. Stannous fluoride 0.351 to 0.474% with an available fluoride ion concentration = 290 ppm for products containing the abrasive calcium pyrophosphate. Preventive Stannous fluoride 0.4% in an anhydrous glycerin gel, treatment made from anhydrous glycerin and the addition of gel suitable thickening agents to adjust viscosity. Treatment rinse Stannous fluoride concentrate marketed in a stable form and containing adequate directions for mixing with water immediately before using to result in a 0.1% aqueous solution.

Dentrifices

Fluoride dentifrices have been shown in numerous clinical trials to be effective anticaries agents [Stookey, J. Dent. Res. 1990, 69(Special Issue): 805-812] and have been recognized as a major cause of the remarkable decline in caries prevalence in many developed countries. Dentifrices have been widely adopted around the world as the principle means of delivering topical fluoride and obtaining caries preventive benefits.

“Washout” of various enamel protectant and enamel repair ingredients from enamel surfaces by saliva flow, eventually controls the effective residence time of various commercial fluoride, enamel protectant and enamel repair, brushing compositions. To improve enamel protectant and enamel repair effectiveness, commercial, professionally prescribed, fluoride, brushing compositions resort to high levels of fluoride, i.e. 5000 ppm for Rx toothpastes, gels and rinses and to approximately 22,000 ppm fluoride for “in-chair”, professionally applied varnishes. In addition, standard OTC, fluoride toothpastes can contain up to 1150 ppm fluoride under the FDA's Fluoride Monograph.

The current market for fluoride brushing products includes: professional and consumer oral care fluoride treatments, both OTC and Rx brushing products; including: toothpastes, gels, pastes and varnishes. As noted above, Rx fluoride toothpastes and Rx fluoride brushing gels are well outside fluoride Monograph levels containing up to 5000 ppm fluoride. Professional oral care, in-chair, fluoride varnishes contain up to about 22,000 ppm fluoride, while OTC fluoride toothpastes can contain up to 1150 ppm total theoretical fluorine, the maximum level provided for by the Monograph.

The American Dental Association (ADA); the Food & Drug Administration (FDA) and oral care professionals including: general practitioners, periodontists, orthodontists, pediatric dentists, etc. as a group; are generally concerned over the trend of increasing fluoride levels. These organizations and oral care professionals generally favor using lower levels of fluoride in various in-chair treatments and various OTC and Rx, oral care, topical, home treatments for patients, provided . . . enamel protection and repair, achieved with lower fluoride levels, are comparable to the results reported for brushing products with higher levels of fluoride. This preference for lower fluoride-brushing products is driven by the concern over toxicity, fluorosis in children, etc., associated with exposure to high fluoride levels, long term.

It is generally accepted, approximately 90% of the fluoride used in OTC and Rx fluoride brushing treatments is expectorated after use. Thus, the window for fluoride treatment of enamel is essentially limited to the time fluoride is being brushed onto the enamel. In contrast, fluoride varnishes containing 22,000 ppm fluoride, applied to the enamel by an oral care professional, are designed to maintain substantive fluoride levels on the enamel after patient expectoration.

Fluoride varnishes are generally applied professionally, at a frequency of about once every six months with the target audience comprising primarily children.

Dietary fluoride levels have gradually increased due to fluoridated drinking water and the fluoride in water used in food preparation, etc. In addition, most consumers use fluoride: toothpastes, rinses, gels, etc. Extensive literature citations indicate topical fluoride treatments are more effective in protecting and repairing enamel than treatment with systemic fluorides.

-   See: Ripa, Public Health Dent., 1991; 51:23-41.

Yet, with all this fluoride available, caries continues to pose a challenge: in children, as well as adults including coronal caries in the elderly, caries in dry mouth patients, caries in immunocompromised patients, caries in patients undergoing medical or dental treatment, etc.

There is a need to improve enamel protectant and enamel repair effectiveness for professional oral care, fluoride treatments, as well as for OTC fluoride products for patient use, while reducing the risk associated with exposure to high fluoride levels.

Additionally, there is a need to improve the efficacy of fluoride products in the area of enamel protection and enamel repair, where the efficacy of various fluoride treatments is assessed as a function of the fluoride level used to effect treatment of various conditions of the enamel.

OBJECTS OF THE PRESENT INVENTION

To provide fluoride brushing gels with improved enamel protectant factor (EPF) values and improved enamel repair factor (ERF) values.

To provide fluoride brushing gels with improved EPF and ERF values, where improvements in EPF and ERF values can be achieved with reduced fluoride content in the brushing gels.

To reduce fluoride levels in brushing gels, while attaining comparable or improved EPF and ERF values, compared to current, commercial, fluoride brushing products, as well as fluoride brushing products described in the prior art.

To improve EPF and ERF brushing gels for “at-risk” patients.

To provide brushing gels that improve challenged enamel conditions of “at-risk” patients including immunocompromised patients; cancer therapy, cardio treatment, diabetes, COP patients; etc.

DEFINITION OF TERMS

The following terms used throughout this specification and claims to describe features of the brushing gels of the present invention are described below:

“Aqueous-free” is defined as: substantially free from water.

“Enamel Protectant Factor (EPF)” is defined as: the percent reduction in enamel solubility divided by the fluoride level in parts per million using FDA method #40.

“Enamel Repair Factor (ERF)” is defined as: the average increase in enamel fluoride concentration divided by the fluoride level of the fluoride brushing product tested using FDA method #33.

“Brushing gel” is defined as: a non-abrasive fluid for administration of stannous fluoride to enamel surfaces.

“Mucoadhesive” is defined as: a substance that is retained for a period of time onto surfaces in the mouth that is not easily removed by the mechanical action of the tongue nor by flow of saliva.

“Stable stannous fluoride” is defined as: compositions that, when chemically assayed, substantially retains the level of stannous and/or fluoride in an unreacted state.

“Biofilm” is defined as: a surface adherent film comprised of bacteria, exuded polysaccharides, etc., that is not easily removed by mechanical means or saliva flow.

“Substantivity agent” is defined as: a composition that improves the mucosal retention of the desired agents.

“Cation bridging” is defined as: electrical attraction between two films or membranes initiated by cation moieties.

“Shift in calcium binding from bidentate to monodentate” is defined as: the loss of “chelate”-like binding by calcium cations with a corresponding increase in single ligand binding by calcium cations.

“Liquid nonionic surfactant” is defined as: a liquid composition that indicates surface active properties with the absence of charged species.

“Solid nonionic surfactant” is defined as: a solid composition that indicates surface active properties with the absence of charged species.

“CaF⁺ moiety” is defined as: a monodentate calcium fluoride ion.

“Linear, polymeric, polycarboxylates, substantivity enhancer” is defined as: a linear polymer with carboxylate substituents that increases retention of compositions onto charged surfaces.

“Emulsion discontinuous phase” is defined as: the minor component in an emulsion that is surrounded by a continuous phase.

“Emulsion continuous phase” is defined as: an emulsion component that surrounds discontinuous phase component.

SUMMARY OF THE INVENTION

The present invention is directed to aqueous-free, brushing gel compositions, wherein the brushing gels contain stannous fluoride and calcium in an aqueous-free, substantivity agent. The brushing gels of the present invention protect and repair enamel more effectively than brushing gels and toothpaste compositions containing comparable or substantially higher levels of fluoride, as indicated by comparative EPF and ERF values reported herein.

The unexpected enamel protectant and enamel repair features of the brushing gels of the present invention, as detailed below in the Examples, Tables and Drawings; are attributed to unique, aqueous-free, brushing gel compositions, which feature:

-   -   (a) stannous fluoride and calcium;     -   (b) a substantivity agent; and     -   (c) cation bridging associated with microbial fluoride binding.

The enamel protectant and enamel repair, brushing gel compositions of the present invention, when brushed onto enamel, form substantive, mucoadhesive gels in the presence of saliva; which mucoadhesive gels gradually release stable stannous fluoride and calcium onto enamel. This slow release continues until the mucoadhesive gel is eventually totally solubilized by saliva. This gradual release minimizes the “wash-out” effect traditionally experienced with fluoride brushing products. The resultant enamel protectant and enamel repair increases in EPF and ERF values, resulting from the extended enamel residence time of stannous fluoride, calcium and cation bridging associated with microbial fluoride binding to biofilm. This improved stannous fluoride efficiency reduces the need to resort to elevated fluoride levels.

Traditionally, fluoride brushing products with strong taste characteristics have been reported to cause excessive salivary stimulation, which increases the rate of fluoride clearance from the mouth. In contrast, the brushing gels of the present invention with exceptionally strong, taste characteristics, including “tingle”, mouthfeel and hedonic characteristics that mask the metallic taste of stannous fluoride; surprisingly indicate increased “residence time” and extend the availability of stannous fluoride, thereby effecting enamel fluoride uptake and enamel protection values (ERF and EPF, respectively) superior to commercial, stannous fluoride, brushing products.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 of the Drawings summarizes comparative, in vitro, enamel protectant factor (EPF) values for enamel treated with a brushing gel of the present invention with stannous fluoride at 970 ppm fluoride, as described in Example 1; compared with: (a) an Rx 5000 ppm, sodium fluoride toothpaste, and (b) an OTC, 1100 ppm, stannous fluoride toothpaste.

FIGS. 2 and 3 of the Drawings illustrate enamel repair factor (ERF) values for brushing gels of the present invention with compositions, as described in Examples 1 and 2; with stannous fluoride at 970 ppm compared with toothpastes having stannous fluoride at 1100 ppm and sodium fluoride at 900 ppm or sodium fluoride at 5000 ppm, respectively.

FIGS. 4 through 6 present ERF values for brushing gels of the present invention comprising compositions, as described in Examples 3 through 5. These brushing gels of the present

DETAILED DESCRIPTION OF THE INVENTION

Aqueous-free, stannous fluoride, calcium, brushing gels of the present invention comprise substantivity agents that contain various enamel protectant and enamel repair ingredients. These substantivity agents function as carriers for various enamel protectant and repair ingredients. These substantivity agents are characterized by their ability, in the presence of saliva, to form mucoadhesive gels which are substantive to enamel with biofilm. These substantive, mucoadhesive gels are further characterized by their ability to: (a) gradually dissolve when exposed to saliva flow, and (b) gradually release various enamel protectant and enamel repair ingredients, in an unreacted state, onto enamel surfaces with biofilm as they dissolve. This gradual dissolution feature of these mucoadhesive gels minimizes saliva “wash-out” of enamel protectant and enamel repair ingredients by gradually releasing these ingredients onto enamel surfaces with biofilm. The substantivity agents of the present invention extend the duration of enamel protectant and enamel repair treatments, and support cation bridging associated with microbial fluoride binding; thereby enhancing the EPF and ERF values of various brushing gels of the present invention, while simultaneously reducing the level of fluoride required to achieve the unexpected increases in EPF and ERF values.

In as preferred embodiment of the invention, phosphate components are also included in the brushing gels. These are described by Ming Tung in U.S. Pat. Nos. 5,037,639; 5,268,167; 5,427,768; 5,437,857; 5,460,803; 5,562,895; by Tung in the American Dental Association Foundation publication, “ACP Technology,”; by Schemehorn, et. al., in The Journal of Clinical Dentistry Vol. XXII: No 2. 51-54, 2011; by the 19 references cited by Schemehorn, et. al.; and by the description of various Gantrez® resins containing calcium, including Gantrez® MS-955 available from International Specialty Products, Wayne, N.J., USA.

The aqueous-free, substantivity agents of the present invention hold the various enamel protectant and enamel repair ingredients, including stannous fluoride, calcium and phosphate components, in a condition where these ingredients remain stable and unreacted. When this aqueous-free, substantivity agent is exposed to saliva, it forms a mucoadhesive gel that is substantive to enamel with biofilm. This mucoadhesive gel continues to hold the enamel protectant and enamel repair ingredients onto enamel surfaces with biofilm without the ingredients reacting. These ingredients eventually react upon being released onto saliva- and biofilm-coated, enamel surfaces.

Eventually, this mucoadhesive, substantivity agent is totally dissolved by saliva, releasing the balance of unreacted enamel protectant and enamel repair ingredients onto saliva- and biofilm-coated, enamel surfaces.

Aqueous-free, brushing gels of the present invention contain enamel protectant and enamel repair ingredients, suitable for protecting and repairing dental enamel; wherein:

-   -   (1) said aqueous-free, brushing gels inhibit premature reaction         of the enamel protectant and enamel repair ingredients;     -   (2) the enamel protectant and enamel repair ingredients are         released onto enamel with biofilm via saliva that solubilizes         substantivity agents that are substantive to: enamel, dentin,         biofilm and pellicle;     -   (3) the enamel protectant and enamel repair ingredients         contained in the substantivity agents are gradually released         onto the enamel in an unreacted state as the saliva soluble,         substantivity agent undergoes saliva dissolution at rates, which         are controlled by saliva flow and the composition of the         substantivity agent; and     -   (4) bidentate binding of calcium shifts to monodentate binding         of calcium in the presence of stannous fluoride.

For purposes of the present invention, saliva soluble, aqueous-free emulsions used as substantivity agents include those emulsions that are comprised of polydimethylsiloxane polymers in solid nonionic surfactants, as described in U.S. Pat. Nos. 5,032,387; 5,098,711; 5,538,667; 5,651,959; having the structural formula:

HO[(C₂H₄O)_(x)/(C₃H₆O)_(y)]—[C₃H₆O]_(z)—[(C₂H₄O)_(x)/(C₃H₆O)_(y)]H

wherein the sum of x, y and z is between 120 and 150. In a preferred embodiment, x=76, y=0 and z=56;

liquid, nonionic surfactants, having the structural formula:

HO[(C₂H₄O)_(x)/(C₃H₆O)_(y)]—[C₃H₆O]_(z)—[(C₂H₄O)_(x)/(C₃H₆O)_(y)]H

wherein the sum of x, y and z is between 125 and 175. In a preferred embodiment, x=76, y=25 and z=56;

and combinations of solid and liquid, nonionic surfactants, wherein the mixture is liquid. The foregoing references are hereby incorporated herein by reference.

In a preferred embodiment of the invention, liquid, nonionic surfactants comprise the continuous phase of the aqueous-free emulsions. These liquid, nonionic surfactants are selected from the group consisting of: poloxamer, having the structural formula set out above, as well as mixtures of such liquid, nonionic surfactants with solid, nonionic surfactants; wherein the mixture is liquid, including: solid, nonionic surfactants having the structural formula set out above.

Preferred aqueous-free, saliva soluble emulsions for use as substantivity agents of the present invention include aqueous-free emulsions comprising a liquid, nonionic, continuous phase and a discontinuous phase of polydimethylsiloxane (PDMS) at viscosities ranging from between about 1500 cs and about 2.5 million cs. Particularly preferred, aqueous-free emulsions include a liquid, nonionic, surfactant, continuous phase and a discontinuous phase PDMS at viscosities between about 10,000 cs and 2.5 million cs.

Solid surfactants, useful as adjuncts to liquid, nonionic, surfactant, continuous phase are described in detail in U.S. Pat. No. 5,651,959. These liquid and liquid/solid, nonionic, surfactant emulsion mixtures are liquid and form mucoadhesive gels in the presence of saliva.

Preferred polydimethylsiloxanes are selected from the group consisting of polydimethylsiloxane: at 1500 cs, at 10,000 cs, at 100,000 cs, at 250,000 cs, at 500,000 cs, at 750,000 cs, at 1.5 million cs, at 2.2 million cs, at 2.5 million cs and combinations thereof.

Foam modulators are useful in the present invention. These include, without limitation: materials operable to control amount, thickness or stability of foam generated by the brushing gel composition upon agitation. Any orally acceptable foam modulator can be used, including polyethylene glycols (PEGs), also known as polyoxyethylenes. High molecular weight PEGs are suitable, including those having an average molecular weight of about 200,000 to about 7,000,000, for example about 500,000 to about 5,000,000 or about 1,000,000 to about 2,500,000. One or more PEGs are optionally present in a total amount of about 0.1% to about 10%, for example about 0.2% to about 5% or about 0.25% to about 2%.

Humectants useful for the brushing gels of the present invention include, without limitation: polyhydric alcohols such as glycerin, sorbitol, xylitol or low molecular weight PEGs. In various embodiments, humectants can prevent hardening of the brushing gels upon exposure to air. In various embodiments, humectants also function as sweeteners.

Any other desired components may be added to the compositions, including, for example, additional: mouth-feel agents, pH modifying agents, flavorants, sweeteners, antimicrobial (e.g., antibacterial) agents such as those described in U.S. Pat. No. 5,776,435, saliva stimulants, anti-inflammatory agents, nutrients, vitamins, proteins, antioxidants, colorants, etc.

invention contain stannous fluoride at a level of 970 ppm, compared with: (a) a 900 ppm sodium fluoride toothpaste, and (b) an 1100 ppm stannous fluoride toothpaste or (c) a 5000 ppm sodium fluoride toothpaste.

Tables 2 through 10 summarize:

-   -   (a) EPF or ERF data for brushing gels of the invention at         varying compositions, as described in Examples 1 through 5,         compared with commercial, fluoride, brushing products;     -   (b) Illustrative Examples of brushing gels of the invention; and     -   (c) Illustrative Treatments with brushing gels of the invention.

In a preferred embodiment, the brushing gels of the present invention contain ingredients that substantially effect enamel protection factor (EPF) and enamel repair factor (ERF) values based on bidentate binding of calcium shifting to monodentate binding of calcium in the presence of stannous fluoride. These include:

-   -   Stannous fluoride, calcium and phosphate components, and     -   Substantivity agents and substantivity enhancers including mixed         sodium and calcium salt copolymers of methyl/vinyl/ether/maleic         acid;     -   wherein the stannous fluoride, calcium and phosphate components         remain unreacted     -   and the pH of the brushing gel when administered to saliva         coated enamel is at least     -   about 3.

The foregoing ingredients are described in detail below.

Stannous Fluoride Concentration

The amount of stannous fluoride in the brushing gels of the present invention, applied to the toothbrush (dose) is not as important as the concentration of available stannous fluoride in the brushing gel. Heretofore, reducing fluoride concentration in brushing products has been reported not to be as effective as regular concentration fluoride products.

-   Petersson, et. al., Swed. Dent. 1982, 6:233-238 -   Metropoulos, et. al., Community Dent. Health, 2002, 1:193-200.

The extraordinary EPF and ERF values of the brushing gels of the present invention allow for reducing stannous fluoride concentrations while effecting acceptable fluoride protection and uptake results.

The fluoride dose is important in regard to enamel fluorosis in children under six years of age, due to fluoride brushing gel ingestion. For this reason, reducing the amount of stannous fluoride applied with the brushing gel of the present invention is a preferred strategy over lowering the dose of stannous fluoride brushing gels of the invention intended for use by children under six years of age.

While fluoride brushing products have a long history of safety, there is a continuing concern associated with dental fluorosis due to fluoride ingestion in children under age six. Dendrys, J. Am. Dent. Assoc. 2000, 131(6): 746-755.

Studies have shown that for children 1-3 years of age, 30 to 75% of the fluoride brushing product is ingested; and for children 4-6 years of age, 14 to 48% is ingested. Warren and Levy, Pediatr. Dent., 199, 21:265-271.

Stannous fluoride brushing gels of the present invention, with their improved efficacy can be used at reduced stannous fluoride levels, and thereby substantially lower the risk of overdosing and the onset of fluorosis, while delivering effective EPF and ERF results.

See also Zero, BMC Oral Health, 2006, 6(Suppl 1): 59; 1-13.

Monitoring the Fluoride-Mineral Phase Formed on Enamel as a Function of the Concentration of Fluoride Ions [F⁻] in the Demineralizing Medium

-   See: Mohammed, et. al., Caries Res., 2013; 47:421-428.     -   At below 45 ppm [F⁻] in the solution ¹⁹F MAS-NMR showed         fluoride-substituted apatite formation, 1B ¹⁹F magic angle,         spinning nuclear magnetic resonance was used to characterize the         solid phase precipitated on enamel as a function of fluoride         concentration during exposure of the enamel to an in vitro         demineralization system. The cariostatic effect of fluoride is         due to the formation of F_(s)a HAP and CaF₂ depending on the         [F⁻] level in the solution.     -   Above 45 ppm, calcium fluoride (CaF₂) is formed in increasing         proportions     -   Further increases in [F⁻] caused no further reduction in         demineralization, but increased the proportion of CaF₂ formed.     -   As to the mechanism of fluoride anticaries efficacy . . .         fluoroapatite formation in enamel is investigated.

Advantages of ¹⁹F MAS-NMR:

-   -   (1) selectively probes the local environment of only fluorine         atoms in the sample, permitting direct identification of the         possible structural forms in which [F⁻] may exist within the         enamel.     -   (2) detects all fluorine present, whether:         -   crystalline,         -   amorphous, or         -   adsorbed.     -   (3) measures very low concentration of fluoride in the order of         0.1%.

¹⁹F MAS-NMR established the effects of varying fluoride concentrations on fluoride-enamel interactions under acidic conditions using bulk enamel blocks rather than powder.

For the samples demineralized in the presence of [F⁻]:

-   -   (1) chemical shifts were identified;     -   (2) formulation of fluoride-substituted apatite:         ^((a))(Ca₁₀CPO₄)₆F_(2-x),         -   (F_(s)-HAP); and     -   (3) formation of CaF2;         -   were observed in approximately aged proportion at 45 ppm             [F⁻] solutions.         -   At [F⁻] above 45 ppm less F_(s)-HAP forms and an increased             signal for CaF         -   For [F⁻] above 136 ppm mostly CaF₂ was identified.

The present study demonstrates that the addition of fluoride produces Fs-HAP as a major chemical species only at low concentrations of fluoride.

There is overwhelming evidence that low fluoride levels found in:

-   -   (a) saliva can significantly reduce enamel demineralization, and     -   (b) plaque has the potential to remineralize even at pH values         typically regarded as demineralizing.

Calcium, CaF₂, CaF⁺ and Phosphate

Tin:

The ability of the tin ions to inhibit plaque formation has been studied primarily using stannous fluoride mouthrinses. Daily rinsing with a 0.1 percent stannous fluoride solution significantly reduces bacterial accumulation on the teeth.

The action of stannous ions is mediated through their ability to bind to lipotechoic acid on the surface of Gram-positive bacterial. The surface net charge of the organisms is therefore reversed and the adsorption of the cells onto teeth is consequently reduced. Furthermore, the effectiveness of stannous fluoride solution in reducing bacterial adhesion is related to the stability of the stannous ions in aqueous solution and the rate at which they are taken up and retained by specific bacteria. The accumulation of tin in bacteria may alter their metabolism and other physiochemical characteristics.

Stannous Fluoride:

This also reduces dentine sensitivity. In solution it undergoes spontaneous hydrolysis and oxidation, so it is applied in the form of a gel mixed with carboxymethylcellulose or glycerin. Stannous fluoride acts as an enzyme poison and may inactivate enzymic activity in the odontoblastic process. Like sodium fluoride, stannous fluoride induces mineralization within the dentinal tubules, which creates a calcific barrier in the dentine surface.

Christofferson, et. al., in ACTA ODONTOL. SCAND. 1988, 46:325-336, reports:

-   -   “It is suggested that the calcium fluoride-like material formed         on dental enamel during treatment of enamel with acidified         solutions of high fluoride content is a phosphate-containing         calcium fluoride.”     -   “The aims of the present work are to determine the rates of         growth and dissolution of pure calcium fluoride in aqueous         suspensions and possible mechanisms controlling these processes,         and to study the properties of the calcium fluoride-like         material formed by adding fluoride to systems containing         hydroxyapatite crystals and/or dissolved calcium and phosphate,         simulating the type of calcium fluoride-like material formed on         dental enamel as a result of topical treatment with acidified         solutions of high fluoride content.”     -   “From our results of dissolution of pure CaF₂ in systems         containing phosphate it can be seen that 1 μm phosphate has a         dramatic effect on the rate of dissolution of CaF₂.”     -   “The calcium fluoride-like materials containing phosphate appear         to be more likely candidates to serve as slow fluoride release         agents.”

B. Øgaard's “CaF₂ Formation: Cariostatic Properties and Factors of Enhancing the Effect,” Caries Res., 2001; 35 (Suppl) 11:40-41, teaches:

-   -   “CaF₂ or a CaF₂-like material/phosphate-contaminated CaF₂ is a         major reaction product during topical treatment of dental hard         tissues. Recently, evidence has suggested that CaF₂ is formed         not only on surfaces but also to some extent in the enamel. The         minimum concentration of fluoride required for CaF₂ formation is         not well known and may depend on whether calcium is available         from plaque fluid or only through dissolution of the dental hard         tissue. Furthermore surface adsorption of fluoride to crystals         may cause local concentrations necessary for CaF₂ formation. It         has been suggested that CaF₂ acts as a pH-controlled reservoir         of fluoride. The rate-controlling factor appears to be         phosphate, which controls the dissolution rate of CaF₂ at high         pH. Increasing fluoride concentration, prolonging the exposure         time or using a fluoride solution with low pH can increase CaF₂         formation. CaF₂ formed at low pH contains less internal         phosphate which has been shown to be less soluble. This may be         of clinical significance for fluoride applied topically a few         times per year.”     -   “The interaction between the fluoride ion and dental hard         tissues has been investigated extensively since modern fluoride         research started in the 1940s. The chemistry of this process is         complicated due to many impurities in hydroxyapatite-like         carbonate and magnesium and to a large variety of fluoride         concentrations, pH and composition of the agents used in caries         prevention. During pH cycling in plaque, fluoride may exchange         with hydroxyl in the apatite and a series of solids with         intermediate composition and crystallographic properties are         formed known as fluorhydroxyapatite.”     -   “CaF₂ is the major or probably the only reaction product on         dental hard tissues from short treatments with relatively         concentrated fluoride agents (Cruz et. al., Scand. J. Dent.         Res., 1992; 100:154-158). Without doubt, this pH-controlled         depot of CaF₂ plays a major role in the cariostatic effect of         topical fluoride. CaF₂ has been detected on dental hard tissues         weeks and months after a single topical fluoride treatment         (Caries Res., 1991, 25:21-26) and is the only logical way to         explain that such treatments have a cariostatic effect. By         treating enamel samples subjected to topical fluoride treatment         with KOH, the cariostatic effect is lost (Øgaard, et al., J.         Dent. Res., 1990, 69:1505-1507).”

J. M. ten Cate's “Review on Fluoride, with special emphasis on calcium fluoride mechanisms in caries prevention”, Eur. J. Oral Sci., 1997, 105:461-465, teaches:

-   -   “For treatments to be effective over periods longer than the         brushing and the following salivary clearance, fluoride needs to         be deposited and slowly released. Calcium fluoride (or like)         deposits act in such a way, owing to a surface covering of         phosphate and/or proteins, which makes the CaF₂ less soluble         under in vivo conditions than in a pure form in inorganic         solutions. Moreover, due to the phosphate groups on the surface         of the calcium fluoride globules, fluoride is assumed to be         released with decreasing pH when the phosphate groups are         protonated in the dental plaque.”     -   “In the presence of low concentrations of fluoride in solution         (such as saliva or plaque fluid), hydroxyapatite might be         dissolved below the critical pH (for hydroxyapatite), but the         released mineral ions could be reprecipitated as fluoroapatite         or a mixed fluor-hydroxyapatite. This mechanism prevents the         loss of mineral ions, while providing additional protection to         mineral crystallites by laying fluoride-rich other layers onto         the apatite crystallites.”     -   “These observations point to the presence of slowly releasing         fluoride reservoirs, either on the dentition or the mucosal         surfaces. Recent work has shown that in particular the oral         mucosa, both by its chemical and morphological nature and the         large surface area, is an underestimated retention site of         fluoride.”     -   “Research has shown that small amounts of fluoride in plaque and         saliva are sufficient to shift the de, remineralization balance         favorably. Such levels should then be available throughout the         day, in particular during periods of carbohydrate fermentation         in the plaque. A fluoride-releasing reservoir system, effective         at low pH, such as shown for calcium fluoride, would be a         preferred system.”

Vogel, et al., in “No Calcium-Fluoride-Like Deposits Detected in Plaque shortly after a Sodium Fluoride Mouthrinse”, Caries Res., 2010; 44:108-115, reported:

-   -   “Plaque ‘calcium-fluoride-like’ (CaF2-like) and fluoride         deposits held by biological/bacterial calcium fluoride (Ca—F)         bonds appear to be the source of cariostatic concentration of         fluoride in plaque fluid. The aim of this study was to quantify         the amounts of plaque fluoride held in these reservoirs after a         sodium fluoride rinse.”     -   “The results suggest that either CaF2-like deposits were not         formed in plaque or, if these deposits had been formed, they         were rapidly lost. The inability to form persistent amounts of         CaF₂-like deposits in plaque may account for the relatively         rapid loss of plaque fluid fluoride after the use of         conventional fluoride dentifrices or rinses.”     -   “Based on laboratory [Margolis and Moreno, J. Dent. Res., 1990,         69 (Spec. Issue) 606-613; J. Am. Dent. Assoc., 2000, 13:887-889;         and clinical observations (reviewed by Featherstone, J. American         Dent. Assoc., 2000, 13:887-889; the current models for         increasing the anticaries effects of fluoride (F) agents         emphasize the importance of maintaining a cariostatic         concentration of F in oral fluids.”     -   “This inability to form potentially more persistent calcium         fluoride deposits, which appears to be due to the low         concentration of oral fluid Ca, may account for the relatively         rapid loss of F in plaque after the use of current         over-the-counter topical F agents. It should be noted in this         regard that (1) studies in which a Ca preapplication was used to         ameliorate this situation have produced very large and         persistent increases in both plaque fluid and that salivary         fluoride (Vogel, et. al., Caries Res., 2006, 40:449-454; Vogel,         et. al., Caries Res. 2008 (a) 421; 401-404; and Vogel, et.         al., J. Dent. Res. 2008(b) 87:466-469; and that (2) preliminary         studies (unpubl.) using modifications of the techniques         described here confirm that the use of a Ca prerinse prior to a         F rinse indeed forms large amounts of CaF₂-like deposits.”

Substantivity Agents

For purposes of the present invention, substantivity agent refers to a composition or combination of compositions that, when administered to oral cavity surfaces with biofilm, enhance the retention of stannous fluoride and calcium to said oral cavity surfaces.

The unexpected enamel protectant and enamel repair features of the aqueous-free, brushing gels of the present invention are attributed to the unique substantivity properties indicated by the brushing gels of the invention.

For purposes of the present invention, preferred substantivity agents for the brushing gels of the present invention include various aqueous-free emulsions of polydimethylsiloxane/polymers in nonionic surfactants at viscosities of at least about 10,000 cs.

These substantivity agents form mucoadhesive gels in the presence of saliva, which are substantive to biofilm-coated enamel and gradually dissolve under saliva flow, releasing stannous fluoride onto the biofilm on the enamel at a pH of at least about 3; thereby effecting EP F and ERF values of at least about 2.5 and about 200, respectively.

For purposes of the present invention, substantivity agents include saliva soluble, aqueous-free emulsions comprised of:

polydimethylsiloxane polymers in solid, nonionic surfactants, as described in U.S. Pat. Nos. 5,032,387; 5,098,711; 5,538,667; 5,645,841; 5,651,959; having the following structural formula:

HO[(C₂H₄O)_(x)/(C₃H₆O)_(y)]—[C₃H₆O]_(z)—[(C₂H₄O)_(x)/(C₃H₆O)_(y)]H

wherein y=0 and the sum of x and z is between 120 and 150. In a preferred embodiment, x=76, y=0 and z=56;

and liquid nonionic surfactants having the following structural formula:

HO[(C₂H₄O)_(x)/(C₃H₆O)_(y)]—[C₃H₆O]_(z)—[(C₂H₄O)_(x)/(C₃H₆O)_(y)]H

wherein the sum of x, y and z is between 125 and 175. In a preferred embodiment, x=76, y=25 and z=56.

Combinations of solid and liquid, nonionic surfactants are also suitable for purposes of the present invention, provided the resultant emulsion remains liquid. All of the foregoing references are hereby incorporated herein by reference.

In a preferred embodiment of the invention, liquid nonionic surfactants comprise the continuous phase of the aqueous-free emulsions. Preferred liquid nonionic surfactants are represented by the structural formula:

HO[(C₂H₄O)_(x)/(C₃H₆O)_(y)]—[C₃H₆O]_(z)—[(C₂H₄O)_(x)/(C₃H₆O)_(y)]H

wherein x=76, v=26 and z=56.

Combinations of liquid, nonionic surfactants with solid, nonionic surfactants are also preferred, including solid nonionic surfactants having the structural formula:

HO[(C₂H₄O)_(x)/(C₃H₆O)_(y)]—[C₃H₆O]_(z)—[(C₂H₄O)_(x)/(C₃H₆O)_(y)]H

wherein x=76, y=0 and z=56, are suitable.

Preferred aqueous-free, saliva soluble emulsions for use in the substantivity agents of the present invention include aqueous-free emulsions comprising a liquid, nonionic, continuous phase and a discontinuous phase of polydimethylsiloxane (PDMS) at viscosities ranging from between about 1500 cs and about 2.5 million cs. Particularly preferred are aqueous-free emulsions with a liquid, nonionic surfactant continuous phase and a discontinuous PDMS phase at viscosities between 10,000 cs and 2.5 million cs. Solid surfactants, useful as adjuncts to the liquid nonionic surfactant continuous phase are described in detail in U.S. Pat. No. 5,651,959. These liquid and liquid/solid nonionic surfactant emulsions form mucoadhesive gels in the presence of saliva.

Preferred polydimethylsiloxanes are selected from the group consisting of polydimethylsiloxane: at 1500 cs, at 10,000 cs, at 100,000 cs, at 250,000 cs, at 500,000 cs, at 750,000 cs, at 1.5 million cs, at 2.2 million cs, at 2.5 million cs and combinations thereof.

In a preferred embodiment of the invention, copolymers described below are useful as substantivity enhancers; when combined with the aqueous-free, substantivity agents of the present invention. These substantivity enhancers include various linear polymeric, polycarboxylates, such as: copolymers of sodium and calcium salts of methyl/vinyl/ether/maleic acid including those copolymers available commercially as Gantrez® MS-955 polymer, a mixed sodium and calcium salt of methyl/vinyl/ether/maleic acid copolymer; where the cations form salt bridges which cross-link the polymer chains.

The chemical structure of this copolymer is represented by the following chemical structure:

where m is an integer that provides molecular weight for the polymer between about 60,000 and about 500,000.

Preferred are 1:4 to 4:1 copolymers of maleic anhydride or acid with another polymerizable ethylenically unsaturated monomer, preferably methyl vinyl ether (maleic anhydride) having a molecular weight of about 30,000 to about 1,000,000.

Sodium and calcium salts of carboxymethyl cellulose ether polymers can also be used including sodium and calcium salts of carboxymethyl cellulose ether, hydroxyethyl cellulose ether, sodium cellulose ether, etc.

The contribution of Ca⁺⁺ from the copolymer substantivity enhancer to ERF values is illustrated in FIGS. 5 and 6 of the Drawings and Tables 6 and 7.

Examples 1 Through 5

The following stannous fluoride brushing gel samples were prepared, as described below, and subsequently tested for EPF and/or ERF values, as described in Tables 2 through 8 below:

Examples 1 and 2 Example 1

In a stainless steel 1 L mixing vessel, using an overhead stirrer, 26.966 gm of PEG 400 were added along with 82.768 gm of glycerin, and 48.78 gm of 1.64% stannous fluoride in glycerin. Stirring was begun at a low speed while heating to 80° C. Then 2.84 gm of L-1220/2.5 million cs (10%) ULTRAMULSION® substantivity agent was added with stirring for 15 minutes. The overhead stirrer speed was increased to medium and 1.88 gm of Gantrez MS-955 substantivity enhancer was added with stirring for 5 minutes. Then Crodasinic L, 1.42 gm; Sucralose, 0.18 gm; and insoluble saccharin, 0.56 gm were added with continued stirring for 10 minutes. TEGO betaine CKD, 1.42 gm, was added and stirred for 5 minutes. Calcium fumarate, anhydrous, micronized, 2.84 gm, was added with stirring for 5 minutes followed by addition of sodium dihydogen phosphate, anhydrous, micronized, 0.612 gm, was added with continued stirring for 5 minutes.

In multiple increments, Sipernat 22S, 28.3 gm was added with stirring 2 minutes between each addition. When the Sipernat 22S was all added, stirring continued for 15 minutes after which Vanillamint, 1.32 gm, and Multisensate flavor, 0.114 gm, were added with continued stirring for 5 minutes. The stirrer was removed and the gel was filled into dispensing tubes. When used as a brushing gel, a pleasant, refreshing mouthfeel and very little metallic taste is perceived.

Example 2

Using the procedure described in Example 1, a second brushing gel was formulated without the Gantrez MS-955 substantivity enhancer.

Examples 3 Through 5

Three STANNOUS FLUORIDE BRUSHING GEL formulations, described below, were prepared using the method described above for Examples 1 and 2. These brushing gel formulations were in vitro tested. The results are reported in Tables 5 through 7 and in

FIGS. 4 through 6 of the Drawings.

Example 3 Stannous Fluoride Brushing Gel

Ingredients Percent Grams PEG 400 13.653 68.265 Glycerin 41.384 206.92 1.64% Stannous Fluoride in Glycerin 24.39 121.95 L-1220/2.5 million CS ULTRAMULSION ® 10% 1.42 7.1 (substantivity agent) Multisensate (flavor enhancer) 0.057 0.285 Gantrez MS-955 (substantivity agent) 0.94 4.7 Vanillamint P 0.66 3.3 Insoluble Saccharin 0.28 1.4 Tego Betaine CKD 0.71 3.55 Sipernat 228 14.15 70.75 Crodasinic L 0.71 3.55 Sucralose 0.09 0.45 Calcium Sulfate 1.25 6.25 Sodium Phosphate Monobasic Anhy. 0.306 1.53 Total 100 100

Example 4 Stannous Fluoride Brushing Gel

Ingredients Percent Grams PEG 400 13.483 67.415 Glycerin 41.384 206.92 1.64% Stannous Fluoride in Glycerin 24.39 121.95 2.5 million CS ULTRAMULSION ® 10% 1.42 7.1 (substantivity agent) Multisensate (flavor enhancer) 0.057 0.285 Gantrez MS-955 (substantivity agent) 0.94 4.7 Vanillamint P 0.66 3.3 Insoluble Saccharin 0.28 1.4 Tego Betaine CKD 0.71 3.55 Sipernat 228 14.15 70.75 Crodasinic L 0.71 3.55 Sucralose 0.09 0.45 Calcium Fumarate 1.42 7.1 Sodium Phosphate Monobasic Anhy. 0.306 1.53 Total 100 100

Example 5 Stannous Fluoride Brushing Gel

Ingredients Percent Grams PEG 400 15.149 75.745 Glycerin 42.384 211.92 1.64% Stannous Fluoride in Glycerin 24.39 121.95 L-1220/2.5 million CS ULTRAMULSION ® 10% 1.42 7.1 (substantivity agent) Multisensate (flavor enhancer) 0.057 0.285 Vanillamint P 0.66 3.3 Insoluble Saccharin 0.28 1.4 Tego Betaine CKD 0.71 3.55 Sipernat 228 14.15 70.75 Crodasinic L 0.71 3.55 Sucralose 0.09 0.45 Total 100 100

In Vitro Testing

In vitro determination of EPF values attributed to administration of various fluoride containing: toothpastes and a test brushing gel onto human enamel subjected to acid challenge.

The following study was carried out according to the FDA Monograph on Anticaries Drug Products for over-the-counter, human use. The study was performed following FDA good laboratory practices.

Purpose of the following in vitro study: to determine the effect of acid challenge to human enamel treated with various fluoride containing brushing products. The effect of the acid challenge was established by measuring the resistance of enamel specimens treated with various fluoride brushing products to an acid challenge; before and after treatment with various fluoride brushing products.

Tooth Preparation:

Three sound human molars were placed in a disc of red boxing wax so that only the enamel surfaces were exposed. Twelve set of three teeth each were prepared for the study. All specimens were cleaned and polished with a flour of pumice slurry and a rag wheel to remove any deposits or stains.

Preparation of Buffered Lactic Acid Challenge Solution:

Two moles (203.58 g of 88.5% pure lactic acid were diluted with approximately 500 ml of distilled water. To this was added a solution of 84 g NaOH dissolved in about 600 ml of distilled water. The total volume was then adjusted to 2000 ml. This was the buffered 1.0 M lactic acid challenge solution.

Another lactic acid solution was prepared by diluting two moles lactic acid to 2000 ml with distilled water. The solution of lactic acid and sodium hydroxide was placed in a 4000 ml beaker, and pH electrodes placed in the solution. The 1.0 M lactic acid solution was used to adjust the pH of the buffered solution to 4.5. To obtain a 0.1 working concentration (for all decalcifications) the 1.0 M buffer was diluted by a factor of 10 with distilled water.

Deprotection:

Before every use, any residual anti-solubility protection afforded by the previous treatment was eliminated. Deprotection of these specimens was accomplished by etching the teeth in the above prepared 0.1M lactate buffer solution for a two-hour period. Each disc of three specimens was agitated (450 rpm) in about 50 ml of lactate buffer at room temperature during the deprotection period. The teeth were rinsed well with distilled water immediately following deprotection.

Pre-Treatment Etch:

The test was performed using preheated (37° C.) tooth sets and lactate buffer. The deprotected tooth sets were mounted on ¼ inch diameter acrylic rods with molten red boxing wax. Multiplaced stirrers were used for treatments and the etches. All slurries and solutions were pre-heated to 37° C. The actual treatments and etches were carried out on the bench top with the preheated solutions. Plastic specimen containers (120 ml) were used for the etching procedure. A ¼ inch hole was drilled in each container lid to accommodate the plastic rod to which the tooth sets were mounted. A 40 ml portion of 0.1M lactic acid buffer was placed in each container along with a one-inch magnetic stirring bar. The rod of the first tooth set was pushed through the hole in the lid, placed in the first container and adjusted so that all enamel surfaces were immersed into the buffer solution. The container was then placed on the first magnetic stirrer and stirring was begun. The timer was started at this time. At 30-second intervals the other tooth sets were started in the same manner. After 15 minutes of exposure to the buffered lactate solution, the first set was stopped and the lid and tooth set immediately removed from the container and placed in a tray of distilled water to terminate etching. The other sets were similarly removed at 30 second intervals in the same order that they were initiated and the lactate buffer solutions was retained for phosphorus analysis. The tooth sets were placed back in the 37° C. water bath in preparation for the fluoride treatment step.

Treatment:

The treatments were performed using slurries of the fluoride brushing products. The slurries consisted of 1 part fluoride brushing product and 3 parts preheated (37° C.) distilled water (9 g:27 ml). Each slurry was mixed for exactly one minute after adding the water. The slurries were NOT prepared ahead of time. They were NOT centrifuged. All tooth sets were treated at the same time (one for each fluoride brushing product). The treatment procedure was similar to the etching procedure with the exception of the slurry in place of the acid. A 30 ml portion of the preheated fluoride brushing slurry was added to the first tooth set, the teeth were immersed in the slurry and the container placed on the first stirrer. The stirrer and timer were started. At 90-second intervals (to allow time for stirring), the other tooth sets were started in the same manner. At the end of the five minutes of treatment, the first set was stopped, the tooth set removed and rinsed well with distilled water. The other sets were removed at 90-second intervals and rinsed well. The treatment fluoride brushing slurries were discarded.

Post-Treatment:

A second acid exposure was then performed by the same method as the pre-treatment etch and the lactate buffer solutions were again retained for phosphorus analysis. The pre and post-treatment solutions were analyzed using a Klett-Summerson Photoelectric Colorimeter.

Repeat Analyses:

The tooth sets were deprotected and the procedure repeated additional times so that each fluoride brushing product was treated and assayed on each tooth set. The treatment design was a Latin Square design so that no treatment followed another treatment consistently.

Calculation of Enamel Solubility Reduction:

The percent of enamel solubility reduction was computed as the difference between the amount of phosphorus in the pre and post acidic solutions, divided by the amount of phosphorus in the pre solution and multiplied by 100.

Treatment Groups:

A. Placebo (deionized water)

B. Positive control 1 Crest® PRO-HEALTH® Toothpaste with stannous fluoride @ 1100 ppm

-   -   fluoride

C. Positive control 2 ClinPro® 5000 Toothpaste with sodium fluoride at 5000 ppm fluoride

D. Test Gel with stannous fluoride at 970 ppm fluoride composition as described hereinafter in Example 1.

Statistical Analyses:

Statistical analyses of the individual means were performed with a one-way analysis of variance model using Sigma Stat (3.1) Software. Since the ANOVA indicated significant differences, the individual means were analyzed by the Student Newman-Keuls (SNK) test.

Results and Discussion:

The deionized water negative control was not effective in reducing enamel solubility. The positive fluoride containing controls and the test gel were significantly more effective than the deionized water negative control. The Clinpro 5000® toothpaste was significantly more effective than the negative control. The Test Gel was significantly more effective than the other two positive controls in reducing enamel solubility.

The results are shown in Table 2 below:

TABLE 2 ENAMEL SOLUBILITY REDUCTION Summary of Results Pre-Etch Post-Etch Delta Percent Group Treatment μP μP μP Reduction EPF ** A Deionized Water  583 ± 24* 633 ± 22 −50 ± 13 −9.06 ± 2.28 — B Crest ® PRO-HEALTH ® 645 ± 23 488 ± 14 158 ± 18 23.83 ± 2.27 2.2 (stannous fluoride @ 1100) C Clinpro 5000 ® (sodium 617 ± 21 582 ± 21  35 ± 14  5.49 ± 2.28 0.1 fluoride @ 5000 ppm) D Brushing Gel (stannous 654 ± 39 409 ± 12 245 ± 32 35.79 ± 2.91 3.7 fluoride @ 970 ppm fluoride) used in a method of treatment of the present invention See Example 1 *Mean ± SEM (N = 12) ** To establish the enamel protection factor (EPF) values for each fluoride brushing product tested, the percent reduction in enamel solubility was divided by the fluoride level in parts per million of the brushing product tested. The resultant number was multiplied by 100. See FIG. 1 of the Drawings.

In Vitro Determination of ERF Values Attributed to Administration of Various Fluoride Containing Toothpastes and a Brushing Gel of the Present Invention onto Incipient Enamel Lesions in Bovine Enamel.

The following study was carried out according to the FDA Monograph on Anticaries Drug Products for over-the-counter, human use, following FDA good laboratory practices.

Purpose of the following in vitro study: to determine the fluoride uptake into incipient enamel lesions in bovine incisors, treated with various fluoride containing, brushing products.

The test procedure was identical to the procedure identified as Procedure 40 in the FDA anticaries Monograph, except the lesions were formed using a solution comprising 0.1 M lactic acid and 0.2% Carbopol 907, wherein the solution was saturated with HAP (hydroxyapatite) at a pH of 5.0.

The fluoride uptake was established by analyzing fluoride and calcium levels of enamel pre-treatment and enamel post-treatment to determine the change in enamel fluoride attributed to treatment with fluoride containing brushing products.

Procedure:

Sound, upper, central, bovine incisors were selected and cleaned of all adhering soft tissue. A core of enamel 3 mm in diameter was prepared from each tooth by cutting perpendicularly to the labial surface with a hollow-core diamond drill bit. This was performed under water to prevent overheating of the specimens. Each specimen was embedded in the end of a plexiglass rod (¼″ diameter×2″ long) using methylmethacrylate. The excess acrylic was cut away exposing the enamel surface. The enamel specimens were polished with 600 grit wet/dry paper and then micro-fine Gamma Alumina. The resulting specimens were a 3 mm disk of enamel with all but the exposed surface covered with acrylic. Twelve specimens per group were prepared.

Each enamel specimen was then etched by immersion into 0.5 ml of 1M HClO₄ for 15 seconds. Throughout the etch period, the etch solutions were continuously agitated. A sample of each solution was then buffered with TISAB (fluoride ion probe buffer) to a pH of 5.2 (0.25 ml sample, 0.5 ml TISAB and 0.25 ml 1N NaOH) and the fluoride content of the solution determined by comparison to a similarly prepared standard curve (1 ml std+1 ml TISAB). For use in depth of each calculation, the Ca content of the etch solution was determined by taking 50 μl and analyzing for Ca by atomic absorption (0.05 ml qs to 5 ml). These data was the indigenous fluoride level of each specimen prior to treatment.

The specimens were once again ground and polished as described above. An incipient lesion was formed in each enamel specimen by immersion into a 0.1M lactic acid/0.2% Carbopol 907 solution for 24 hours at room temperature. These specimens were then rinsed well with distilled water and stored in a humid environment until used.

The treatments were performed using slurries of the various fluoride containing brushing products. The flurries consisted of 1 part fluoride containing brushing product and 3 parts distilled water (9 g:27 ml). Each slurry was mixed for exactly one minute after adding the water. The slurries were NOT prepared ahead of time. They were NOT centrifuged. The 12 specimens of each group were then immersed into 25 ml of their assigned slurry with constant stirring (350 rpm) for 30 minutes. Following treatment, the specimens were rinsed with distilled water. One layer of enamel was then removed from each specimen and analyzed for fluoride and calcium as outlined above (i.e. 15 second etch). The pretreatment fluoride (indigenous) level of each specimen was then subtracted from post treatment, fluoride value to determine the change in enamel fluoride due to the last treatment.

Statistical Analyses:

All raw data (individual specimen Enamel Fluoride Uptake (EFU) values wee reported. In addition, the mean, S.D. (standard deviation) and SEM (scanning electron micrograph) for each group was calculated. Statistical analysis were performed by a one-way analysis of variance model using Sigma Stat Software (3.1). Since significant differences are indicated, the individual means were analyzed by the Student Newman Keuls (SNK) test.

Test Products:

The test fluoride containing brushing products were coded as follows:

-   -   1. Placebo (deionized water)     -   2. Positive Control 1 Crest® PRO-HEALTH® with stannous fluoride         at 1100 ppm fluoride     -   3. Positive control 2 Clinpro 5000® with sodium fluoride at 5000         ppm fluoride     -   4. Brushing Gel of the present invention with stannous fluoride         at 970 ppm fluoride composition as described in Example 1.

Results:

The results are shown in Table 3 below:

TABLE 3 Change in Incipient Lesion Enamel Fluoride Content Enamel Fluoride Concentration (ppm) Fluoride Containing Pre Post Brushing Product Treatment Treatment Increase Etch Depth ERF*** Placebo, deionized water  41 ± 4*  44 ± 3  3 ± 2 17.88 ± 0.70 — Crest ® PRO-HEALTH ® @ 44 ± 5 1888 ± 81 1843 ± 83 10.06 ± 0.25 170 1100 stannous fluoride Clinpro 5000 ® @ 5000 ppm 52 ± 6 3310 ± 88 3258 ± 88  15.28 ± 0.56** 65 sodium fluoride Brushing Gel @ 970 ppm 47 ± 5  3003 ± 212  2956 ± 212 13.36 ± 0.26 300 stannous fluoride See Example 1 *Mean ± SEM (N = 12) **Values 15.32 and 15.28 are not significantly different ***To establish the enamel repair factor (ERF) values for each fluoride brushing product tested, the increase in enamel fluoride concentration was divided by the fluoride level of the fluoride brushing product. The resultant number was multiplied by 100. See FIG. 2 of the Drawings.

In vitro determination of ERF values attributed to administration of various fluoride containing: toothpastes and a brushing gel of the present invention onto incipient enamel lesions in human enamel was carried out following the Enamel Fluoride protocol described above for the results reported in Table 3. Some of the fluoride containing brushing products tested in this fluoride uptake study are different than those reported on in Table 3 above.

TABLE 4 Change in Incipient Lesion Enamel Fluoride Content Enamel Fluoride Concentration (ppm) Fluoride Containing Pre Post Brushing Product Treatment Treatment Increase Etch Depth ERF** Placebo, deionized  41 ± 4*  89 ± 5  47 ± 5 17.88 ± 0.70 — water Crest ® PRO-HEALTH ® 44 ± 5 1530 ± 69 1486 ± 66 10.06 ± 0.25 140 Toothpaste (stannous fluoride, 1100 ppm fluoride) Brushing Gel (stannous 52 ± 6 2656 ± 80 2615 ± 79 15.26 ± 0.56 270 fluoride at 970 ppm fluoride) See Example 2 *Mean ± SEM (N = 12) **To establish the enamel repair factor (ERF) values for each fluoride brushing product tested, the average increase in enamel fluoride concentration (post treatment was divided by the fluoride level of the fluoride brushing product tested. The resultant number was multiplied by 100). See FIG. 3 of the Drawings

TABLE 5 Change in Incipient Lesion Enamel Fluoride Content Enamel Fluoride Concentration (ppm) Fluoride Containing Pre Post Brushing Product Treatment Treatment Increase Etch Depth ERF** Placebo, deionized  46 ± 4* 56 ± 4  9 ± 4 17.55 ± 0.28 — water Crest ® PRO-HEALTH ® 57 ± 6 2338 ± 73  2280 ± 76   9.51 ± 0.35 210 Toothpaste (stannous fluoride, 1100 ppm fluoride) Brushing Gel (stannous 48 ± 5 3034 ± 117 2987 ± 114 11.15 ± 0.18 380 fluoride at 970 ppm fluoride) See Example 5 *Mean ± SEM (N = 12) **To establish the enamel repair factor (ERF) values for each fluoride brushing product tested, the average increase in enamel fluoride concentration (post treatment was divided by the fluoride level of the fluoride brushing product tested. The resultant number was multiplied by 100). See FIG. 4 of the Drawings.

TABLE 6 Change in Incipient Lesion Enamel Fluoride Content Enamel Fluoride Concentration (ppm) Fluoride Containing Pre Post Brushing Product Treatment Treatment Increase Etch Depth ERF** Placebo, deionized  46 ± 4* 56 ± 4  9 ± 4 17.55 ± 0.28 — water Crest ® PRO-HEALTH ® 57 ± 6 2338 ± 73  2280 ± 76   9.51 ± 0.35 210 Toothpaste (stannous fluoride, 1100 ppm fluoride) Brushing Gel (stannous 56 ± 4 4032 ± 216 3976 ± 217 10.84 ± 0.24 410 fluoride at 970 ppm fluoride) See Example 3 *Mean ± SEM (N = 12) **To establish the enamel repair factor (ERF) values for each fluoride brushing product tested, the average increase in enamel fluoride concentration (post treatment was divided by the fluoride level of the fluoride brushing product tested. The resultant number was multiplied by 100). See FIG. 5 of the Drawings.

TABLE 7 Change in Incipient Lesion Enamel Fluoride Content Enamel Fluoride Concentration (ppm) Fluoride Containing Pre Post Brushing Product Treatment Treatment Increase Etch Depth ERF** Placebo, deionized  46 ± 4* 56 ± 4  9 ± 4 17.55 ± 0.28 — water Crest ® PRO-HEALTH ® 57 ± 6 2338 ± 73  2280 ± 76   9.51 ± 0.35 210 Toothpaste (stannous fluoride, 1100 ppm fluoride) Brushing Gel (stannous 57 ± 5 10462 ± 357 10406 ± 363 13.95 ± 0.39 1070 fluoride at 970 ppm fluoride) See Example 4 *Mean ± SEM (N = 12) **To establish the enamel repair factor (ERF) values for each fluoride brushing product tested, the average increase in enamel fluoride concentration (post treatment was divided by the fluoride level of the fluoride brushing product tested. The resultant number was multiplied by 100). See FIG. 6 of the Drawings.

TABLE 8 Summary of Stannous Fluoride Brushing Gel ERF data, based on using methods of the present invention with various brushing gel compositions, as described in Tables 3 through 7 and in FIGS. 2 through 6 of the Drawings Stannous Fluoride Brushing Gel Substantivity Calcium Phosphate Substantivity Additional Total pH upon described in: Agent SnF2 Content Content Fluoride Enhancer Ca⁺⁺ Ca⁺⁺ application Table No/Fig No. (% by wt.) in PPM

% % Uptake (% by wt) % % to enamel ERF 3/2 L-1220 & PDMS 970 0.369 0.242 2956 0.94 0.1 0.469 4.0 300 (Example 1) 2.5 million cs (1.42) 4/3 L-1220 & PDMS 970 0 0 2615 0 0 0 — 270 (Example 2) 2.5 million cs (1.42) 5/4 L-1220/2.5 million cs 970 0 0 2987 — 0 0 380 (Example 5) ULTRAMULSION ® 10% (1.42) 6/5 L-1220/2.5 million cs 970 1.25 0.306 3976 0.94 0.1 1.35 410 (Example 3) ULTRAMULSION ® 10% (1.42) 7/6 2.5 million cs 970 1.42 0.306 10406 0.94 0.1 1.52 1070 (Example 4) ULTRAMULSION ® 10% (1.42)

indicates data missing or illegible when filed

TABLE 9 Illustrative Examples of Brushing Gels Stannous Fluoride Substantivity Example level in ppm Poloxamer PDMS Enhancer pH of GEL No. fluoride (% by wt.) (% by wt.) (% by wt.) in saliva 6 970 L-1220 (1.8) 2.5 million cs MS-955 3.5 (0.2) (1.1) 7 1100 F-127 (2.7) 800,000 cs MS-955 3.0 (0.3) (0.94) 8 600 L-1220 (2.25) 1.5 million cs MS-955 5.6 (0.25) (0.97) 9 800 L-1220 (1.8) 1.2 million MS-955 4.5 (0.2) (0.94) 10 500 F-127 (2.25) 1 million cs MS-955 5.0 (0.25) (1.0) 11 400 F-127/L-1220 (0.8) 2.5 million cs MS-955 5.8 (0.2) (0.94) 12 1000 F-127/L-1220 (2.85) 2 million cs MS-955 3.7 (0.71) (1.16) 13 700 L-1220 (2.5) 1.8 million cs MS-955 4.8 (0.63) (1.0) 14 850 F-127 (2.1) 2.5 million cs MS-955 4.3 (0.23) (0.94)

TABLE 10 Treatment of “at-risk” patients with Brushing GELS of the Invention Specific Brushing GEL Formulation Frequency of Duration of “At-risk” Patient Recommended Treatment Treatment Children under 7 Example 4 Once daily for 2 To be determined years of age minutes followed by pediatric dentist by expectorating Undergoing medical Example 4 At least twice daily Duration of and/or professional medical/professional oral care treatments oral care treatment with prescribed medications Immunocompromised Example 5 At least twice daily For term of chronic with chronic condition conditions Diabetes, heart Example 3 Several times daily For term of chronic disease, etc. condition Cancer treatment Example 4 As required To be determined by oral care professional

Example 15

A 5 liter Ross/Olsa vacuum mixer with internal homogenizer was heated to 80 degrees C. while the vessel was charged with 647.15 gm of PEG 400, 2069.2 gm of anhydrous glycerin and 1219.5 gm of 1.64% stannous fluoride/glycerin. Anchor stirring at slow speed was begun and continued for 7 minutes. ULTRAMULSION® [(Plurocare L-1220 (90%)) and 2.5 million cs polydimethylsiloxane (10%), 71 gm, was added with homogenizer speed adjusted to 2500 rpm for 15 minutes. The anchor stirrer was increased to medium speed and Gantrez MS-955, 47 gm, was added with stirring and homogenizing for 5 minutes. Crodasinic L, 35.5 gm, was added with continued stirring for 5 minutes. TEGO Betaine CKD, 35.5 gm, was added and stirring continued for 5 minutes. Micronized (20 micron D50) calcium fumarate, anhydrous, 71 gm, was added with stirring for 5 minutes. Micronized (20 micron) sodium phosphate monobasic, anhydrous, 15.3 gm, was added with stirring for 5 minutes. Sident 22S, 707.5 gm, was added in increments at 2 minutes between additions until all was added. Stirring was continued for 15 minutes.

Vanillamint P flavor, 33 gm, and spilanthes extract, 2.85 gm, were added with continued stirring for 5 minutes. The vessel was cooled to ambient temperature over 15 minutes. The contents were dispensed into tubes for use. Upon dispensing, the brushing gel was pleasant testing with no stannous fluoride aftertaste. Stannous fluoride stability testing was performed on the product.

Discussion of EPF and ERF Values Established by In Vitro Testing

The stannous fluoride brushing gels of the present invention show substantial improvement in EPF and ERF values compared to commercial toothpastes at various fluoride levels as reported in: Tables 2 through 7, FIGS. 1 through 6 of the Drawings and Summary Table 8.

For example, the ERF values, reported in Table 3 and FIG. 2 for a Crest® PRO-HEALTH® and Clinpro 5000® toothpastes are 170 and 65 respectively, compared to an ERF for the stannous fluoride brushing gel of the present invention of 300. The ERF values reported in Table 7 and FIG. 6 of the Drawings for Crest® PRO-HEALTH® toothpaste is 210 compared to an ERF for the Stannous Fluoride Brushing Gel of the present invention, 1070.

These 2× and 5× improvements, respectively, in ERF value over commercial toothpastes represent a major advance in fluoride uptake and enamel hardening. Such an advantage in enamel hardening efficiency is particularly critical to children as well as to patients experiencing: rampant caries, coronal caries, cancer therapy treatments, mucositis treatments, immune deficiency treatments, bone marrow transplants, etc.

Proposed Mechanism of Action of the Compositions of the Present Invention

The enamel protectant and/or enamel repair (EPF and/or ERF) data reported for formulations described in Examples 1 through 5, as detailed in Tables 2 through 8 and in FIGS. 1 through 6 of the Drawings, suggest the substantivity of stannous fluoride and calcium to the biofilm present on enamel surfaces is enhanced by a shift from bidentate to monodentate calcium binding in the presence of stannous fluoride. This shift in calcium binding in the presence of stannous fluoride results in a most effective binding site configuration. See:

-   Dudey and Lim, J. Phys. Chem B, 2004, 108:4546. -   Vogel, et. al., Caries Res., 2010, 94:108-115. -   Rolla and Bowen, Scand. J. Dent. Res., 1977; 85:149-151. -   Rose, et. al., J. Dent. Res., 1993; 72:78-84.

See also:

-   Turner, et. al., Ceramics, Silikaty 57(1):1-6 (2013) -   Mohammed, et. al., Caries Res., 47:421-428 (2013)

Calcium-Bridge, Fluoride Binding

Calcium binding to biofilm shifts from a bidentate chelation to a monodentate chelation in the presence of fluoride, freeing up calcium to bind with fluoride, CaF⁺ pair, thereby doubling the calcium binding capacity.

Stable fluoride in the brushing gels of the present invention produces marked reduction in calcium binding affinity and approximately doubles calcium binding capacity. In the absence of fluoride, calcium binding to biofilm is bidentate. Stable fluoride in the brushing gels of the present invention compete with biofilm causing calcium binding to biofilm to become monodentate. This allows the binding of about double the quantity of calcium and of CaF⁺ bound to biofilm. Release of fluoride bound by calcium bridging into biofilm fluid as a result of fluoride clearance into saliva will always be accompanied by a corresponding release of calcium which, in turn, potentiates the cariostatic effect of fluoride as indicated in the in vitro testing described in Tables 2 through 7 and FIGS. 1 through 6 of the Drawings.

At least some of the stable fluoride present in the brushing gels of the present invention is bound to calcium ions (sourced from various calcium salts in the present invention and/or calcium present in the copolymer substantivity enhancer, such as Gantrez® MS-955). These calcium ions, in turn, are bound to biofilm associated with enamel.

A drop in pH follows exposure of plaque to sucrose which removes some anionic groups by neutralization, thereby liberating calcium and fluoride (as CaF⁺) at the very sites where these moieties can do the most good.

The effectiveness of the Brushing Gel compositions of the present invention depends on three factors:

-   -   (1) substantivity of the formulation to biofilm,     -   (2) stannous fluoride as the source of CaF⁺, and     -   (3) retention of fluoride in a form on biofilm which allows         release of CaF⁺ ions into hydroxyapatite.

Stannous fluoride produces a marked reduction in calcium binding affinity accompanied by an approximate doubling of the calcium binding capacity. In the absence of fluoride, divalent cation binding to plaque is bidentate. Fluoride competes with macromolecular anionic groups, causing binding to become monodentate. Release of fluoride formed by calcium bridging, is accompanied by release of calcium, which potentiates the cariostatic effect of fluoride.

The presence CaF⁺ is required to deliver the enamel protection and repair (EPF and ERF) results required for the Brushing Gel formulations of the present invention.

Summary as to the Role of Cation Bridging in Microbial Fluoride Binding

Fluoride binding produces a marked reduction in calcium binding affinity, along with a doubling of calcium binding capacity. This indicates that calcium binding changes from bidentate to monodentate. This shift from bidentate to monodentate is a consequence of fluoride replacing an anionic group as one of the calcium ligends.

The anionic groups to which calcium is no longer bound are then free to bind a CaF⁺ ion pair, resulting in a doubling of the calcium binding capacity. Release of fluoride, bound by calcium bridging into plaque fluid, may be accompanied by a release of calcium which will potentiate the cariostatic effect of fluoride.

CaF⁺ is taken up by hydroxyapatite and is responsible for the EPF and ERF in vitro data reported for the compositions of the present invention. The ERF values reported in Tables 3 through 8 and FIGS. 2 through 6 of the Drawings suggest that the CaF⁺ moiety is incorporated into the hydroxyapatite lattice during remineralization.

The brushing gels of the present invention set a new, oral care standard for Enamel Protection and Enamel Repair, while dramatically reducing exposure to elevated fluoride levels in various fluoride varnishes, gels and toothpastes. 

What is claimed is:
 1. Substantially aqueous-free, enamel protectant and enamel repair, brushing gels containing: stannous fluoride and calcium in a substantivity agent, wherein: (a) Substantivity of said stannous fluoride and calcium into biofilm present on enamel is enhanced through a shift in calcium binding from bidentate to monodentate in the presence of stannous fluoride; (b) EPF and ERF values of at least about 2.5 and 200, respectively, are achieved with periodic administration of said brushing gels onto enamel surfaces with biofilm present.
 2. A composition according to claim 1, wherein said substantivity agent is selected from solid and liquid, nonionic poloxamers and combinations thereof.
 3. A composition according to claim 1, wherein some of said stannous fluoride and calcium is present as CaF⁺.
 4. A composition according to claim 2, wherein said substantivity agent contains linear, polymeric polycarboxylate, substantivity enhancers.
 5. Substantially aqueous-free, enamel protectant and enamel repair, brushing gels according to claim 4, containing stannous fluoride and calcium in a substantivity agent comprising an emulsion of polydimethylsiloxane polymer at viscosities from between about 10,000 cs and about 2.5 million cs as the discontinuous phase in a nonionic, liquid surfactant, continuous phase.
 6. Brushing gels, according to claim 5, wherein nonionic liquid poloxamer surfactants, suitable for said brushing gels, are represented by the structural formula: HO[(C₂H₄O)_(x)/(C₃H₆O)_(y)]—[C₃H₆O]_(z)—[(C₂H₄O)_(x)/(C₃H₆O)_(y)]H wherein the sum of x, y and z is from between 125 and
 175. 7. Brushing gels, according to claim 4, wherein nonionic liquid surfactants, suitable for said brushing gels, are represented by the structural formula: HO[(C₂H₄O)_(x)/(C₃H₆O)_(y)]—[C₃H₆O]_(z)—[(C₂H₄O)_(x)/(C₃H₆O)_(y)]H wherein x=76, y=25 and z=56.
 8. Brushing gels, according claim 1, containing unreacted, calcium and phosphate components.
 9. Substantially aqueous-free, enamel protectant and enamel repair, brushing gels containing stannous fluoride and calcium in a substantivity agent comprising an emulsion of polydimethylsiloxane polymer at viscosities from between about 10,000 cs and about 2.5 million cs as the discontinuous phase in a nonionic, solid poloxamer surfactant, continuous phase and a linear polymeric polycarboxylates substantivity enhancer.
 10. Brushing gels, according to claim 9, wherein nonionic, solid, poloxamer surfactants, suitable for said brushing gels, are represented by the structural formula: HO[(C₂H₄O)_(x)/(C₃H₆O)_(y)]—[C₃H₆O]_(z)—[(C₂H₄O)_(x)/(C₃H₆O)_(y)]H wherein the sum of x, y and z is from between 120 and
 150. 11. Brushing gels, according to claim 9, wherein nonionic, solid, poloxamer surfactants, suitable for said brushing gels, are represented by the structural formula: HO[(C₂H₄O)_(x)/(C₃H₆O)_(y)]—[C₃H₆O]_(z)—[(C₂H₄O)_(x)/(C₃H₆O)_(y)]H wherein x=76, y=0 and z=56.
 12. Brushing gels, according claim 9, containing unreacted, calcium and phosphate components.
 13. Brushing gels, according to claim 6, wherein said nonionic surfactant is a liquid surfactant selected from the group consisting of liquid surfactants having the following, general, structural formula: HO[(C₂H₄O)_(x)/(C₃H₆O)_(y)]—[C₃H₆O]_(z)—[(C₂H₄O)_(x)/(C₃H₆O)_(y)]H wherein the sum of x, y and z is from between 125 and
 175. 14. Substantially, aqueous-free, enamel protectant and enamel repair, brushing gels, featuring monodentate-bidentate bonding of calcium in the presence of stannous fluoride; containing: stannous fluoride, calcium and phosphate components, and a substantivity agent emulsion containing liquid, nonionic, poloxamer surfactant as the continuous phase and polydimethylsiloxane polymer as the discontinuous phase; with an EPF of at least about 2.5 and ERF of at least about
 200. 15. Brushing gels, according to claim 6, wherein said polydimethylsiloxane polymer discontinuous phase comprises up to 40% of said emulsion.
 16. Substantially aqueous-free, enamel protectant and enamel repair, brushing gels containing stable stannous fluoride and calcium on a substantivity agent substantive to biofilm coated enamel, wherein: (a) substantivity of said stannous fluoride and calcium into said biofilm is enhanced by a substantivity enhancer and by a shift from bidentate binding of calcium to monodentate in the presence of stable stannous fluoride; and (b) said stannous fluoride, upon release from said substantivity agent, converts to the moiety CaF⁺ which effects EPF and ERF values of at least about 2.5 and about 200, respectively.
 17. Brushing gels according to claim 1, wherein said stannous fluoride, upon release from said substantivity agent, includes a CaF⁺ moiety in the presence of said calcium monodentate binding to said biofilm present on enamel.
 18. Brushing gels according to claim 1, wherein the pH of said brushing gel, upon administration to enamel with biofilm, is at least about
 3. 19. Brushing gels according to claim 4, wherein the level of said substantivity agent and said substantivity enhancers is between about 0.5 and about 5% by wt. and about 0.1 and about 3% by wt., respectively.
 20. Brushing gels according to claim 1, wherein said EPF and ERF values range from between about 380 and about
 1070. 21. Brushing gels according to claim 1, wherein said calcium is selected from the group of calcium compositions comprising: calcium fumarate, calcium sulfate, calcium gluconate, mixed sodium and calcium salts of methyl/vinyl/ether/maleic copolymers and combinations thereof.
 22. Brushing gels according to claim 4, wherein said substantivity enhancer has the structural formula:

where m is an integer that provides weight between about 60,000 and about 1,000,000.
 23. Brushing gels according to claim 1, wherein the total calcium level is between about 0.5 and about 5.0. 